A jaundiced infant at 12 hours of an RhD-sensitised pregnancy — OSCE

Candidate brief

You are the neonatal registrar reviewing a term infant 12 hours after birth. The mother is Rh-negative with a known anti-D antibody from a previous pregnancy; she received antenatal care and the pregnancy was monitored with MCA-PSV Doppler. The infant's birth weight is 3300 grams, the temperature is 36.8 degrees, and the infant is visibly jaundiced to the mid-trunk. The cord blood shows a positive direct antiglobulin test, a haemoglobin of 105 g per litre, and the serum bilirubin is 220 micromoles per litre and rising. The infant is alert and feeding. [5]

Task

1. State the diagnosis and interpret the bilirubin against the hour-specific nomogram for this infant's age and risk factors. [5] [6]
2. Outline the immediate management, including the phototherapy, IVIG and exchange transfusion steps and their thresholds. [5] [8]
3. Describe the investigations you would send to characterise the haemolysis, and the surveillance over the first days. [5]
4. Outline the anticipated complications and the follow-up, including late anaemia and audiology. [4]

Examiner discussion points

• Why does jaundice in the first 24 hours demand investigation for haemolysis? It is never physiological; the direct antiglobulin test, blood count and film, and blood groups identify the mechanism. [5]
• How does haemolysis change the bilirubin thresholds? It is itself a risk factor that lowers the phototherapy and exchange thresholds on the hour-specific nomogram, so the infant reaches intervention earlier than a non-haemolysing peer. [5] [6]
• When would you add IVIG, and what is the dose? When haemolysis is confirmed and the bilirubin continues to rise toward exchange despite intensive phototherapy; IVIG 0.5 to 1 g per kilogram blocks Fc receptors on splenic macrophages. [8]
• What does exchange transfusion achieve that the other measures do not? It simultaneously removes antibody-coated red cells, bilirubin and antibody, replacing them with compatible donor cells — a triple action beyond phototherapy and IVIG. [5]

Key teaching points

The case turns the IgG-mediated mechanism into a sequence of decisions: recognise first-24-hour jaundice as haemolysis, plot the bilirubin against the hour-specific nomogram, start intensive phototherapy early, add IVIG when the rise continues toward exchange, and perform exchange transfusion at the threshold or with signs of acute bilirubin encephalopathy. The prevention of bilirubin neurotoxicity is built into every step, and late anaemia and audiology follow-up complete the care of the affected infant and the family. [5] [8]